The Cancel Reservation option allows you to change the arrival and/or departure date of a reservation, change the unit the reservation is in, change the dollar amounts charged or cancel the reservation. If a reservation is changed from one unit to another, the unit first booked will become available and the new unit, which must have been available, will be booked. If a reservation has actually arrived and stayed in the first unit for a period of time you would normally shorten the existing reservation to the actual stay and create a second reservation for the stay in the second unit. This would allow income to be posted to both units owner statements. In this case you would normally debit the first reservation the amount "overpaid" putting it into (crediting) an offset account and credit the new reservation the amount "owed" pulling (debiting) the money from the offset account. This effectively transfers money from one reservation to another.
See Also Change or Cancel Reservation
"How do I charge a penalty fee for a cancelled reservation?"